1. Technical Field
The present invention relates to a droplet discharge device including a discharge head having a discharge nozzle for discharging a droplet, and a droplet discharge method by the droplet discharge device.
2. Related Art
As a technique of forming a functional film such as a color filter of a color liquid crystal device, the following technique of forming a functional film by using a droplet discharge device is known. The droplet discharge device is provided with a droplet discharge head which discharges a droplet as droplets. In the technique, a droplet containing a material of the functional film is discharged as droplets so as to land on an arbitrary position on a substrate which serves as a processing object. Thus the droplet is arranged on the arbitrary position. Then, in the technique, the droplet arranged is dried so as to form the functional film. The droplet discharge head of the droplet discharge device used in such film formation can selectively discharge a minute droplet from its discharge nozzle and allow the droplet to land with a high positional accuracy so as to be able to form a film having a precise planar shape and a precise film thickness.
In order to form a functional film with higher functionality, it is required to realize a functional film having more precise planar shape and more precise film thickness. In order to form a functional film having a uniform film thickness, it is required to maintain a constant discharge amount of a functional liquid discharged from a discharge nozzle. The discharge amount means a size (volume) of a droplet discharged from the droplet discharge head or an amount discharged in a unit time from the discharge head which performs continuous discharge. A weight of a functional liquid corresponding to the discharge amount is referred to as a discharge weight. Discharge of a droplet toward a processing object is referred to as drawing discharge, and an approximate continuous discharge step including the drawing discharge is referred to as a drawing discharge step.
It is known that a viscosity of a droplet varies depending on a temperature. In a droplet discharge device, the variation of viscosity of the droplet varies flow resistance of the droplet, so that there is a possibility that the discharge amount varies. That is, there has been such a problem that the discharge amount from the droplet discharge device varies due to the variation of the temperature of the discharge device.
JP-A-2004-209429 as an example discloses a droplet discharge system that realizes a uniform discharge amount. The system realizes the uniform discharge amount such that a droplet discharge device is disposed in a chamber so as to maintain a temperature of the atmosphere approximately constant, and at the same time, a discharge weight is measured so as to adjust the discharge amount depending on the measurement result.
However, various driving sources for driving the discharge device of the droplet discharge device release heat as a heat source in many cases, so that the sources highly likely vary the temperature of the discharge device. Further, there is a possibility that a member that generates no heat such as a processing object and a droplet which is to be supplied to the discharged device absorbs heat, possibly varying the temperature of the discharge device. Even though the temperature of the atmosphere is maintained approximately constant as the droplet discharge system disclosed in the above example, there is a possibility that temperatures of the discharge device and the droplet vary during the drawing discharge step in which the processing object and the droplet are supplied and the discharge device is driven. The discharge amount may vary during the drawing discharge step due to the variation of the temperature during the drawing discharge step. In the same manner, the temperatures of the discharge device and the droplet may different between in the drawing discharge step and in the measurement of the discharge weight. Due to the difference, there is a possibility that the discharge amount obtained by measuring the discharge weight is not always a precise discharge amount in the drawing discharge step.